Biodiesel has long been known as an alternative diesel fuel. Typically, the biodiesel was used to replace hydrocarbonaceous diesel fuel. Blends of biodiesel and hydrocarbonaceous diesel fuels were also prepared in order to obtain a more environmentally friendly fuel.
Sulfur contained in fuel, for example middle distillate fuels such as diesel fuel and jet fuel, is said to constitute a serious environmental hazard. Hence strict regulations limiting the amount of sulfur which may be present in such fuels have been introduced. Unfortunately, fuels having a suitably low sulfur content exhibit very poor inherent lubricity and this can lead to problems when the fuel is used. For example, the use of low sulfur fuel in diesel engines frequently results in damage to the fuel injector pump which relies on the natural lubricating properties of the fuel to prevent component failure. There is therefore a need to improve the lubricating properties of low sulfur fuels.
EP-A-0608149 discloses the use of an ester as an additive in a liquid hydrocarbon compression-ignition fuel oil for reducing consumption of the fuel oil.
EP-B-680506 discloses the use of esters as lubricity additives in low sulfur diesel fuel. The reference does not suggest the use of blends containing derivatives of diethanolamine or teach biodiesel, specifically.
EP-A-0635558 discloses gas oil compositions containing lubricity additives which are lower alkyl esters of a mixture of saturated and unsaturated fatty acids derived from vegetable oleaginous seeds. The reference does not suggest the use of blends containing derivatives of diethanolamine.
U.S. Pat. No. 4,204,481 teaches anti-wear compression ignition fuel comprising a wear inhibiting amount of a fatty acid amide or ester of diethanolamine. The reference does not suggest blending said fatty acid amides or esters with biodiesel.